Runtime evaluation/In an environment: Difference between revisions
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(→{{header|Octave}}: add note about nonglobalness) |
(→{{header|Tcl}}: provide another solution for clarified requirements) |
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=={{header|Tcl}}== |
=={{header|Tcl}}== |
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<lang tcl>package require Tcl 8.5 |
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set x $a |
set x $a |
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set 1st [expr $func] |
set 1st [expr $func] |
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set x $b |
set x $b |
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set 2nd [expr $func] |
set 2nd [expr $func] |
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expr {$2nd - $1st} |
expr {$2nd - $1st} |
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} |
} |
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puts [eval_twice {2 ** $x} 3 5];</lang> |
puts [eval_twice {2 ** $x} 3 5] ;# ==> 24</lang> |
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Here's another take, similar to other answers. It passes a code block to be <code>eval</code>ed, not just an expression for <code>expr</code> |
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<lang tcl>proc eval_with_x {code val1 val2} { |
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expr {[set x $val2; eval $code] - [set x $val1; eval $code]} |
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} |
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eval_with_x {expr {2**$x}} 3 5 ;# ==> 24</lang> |
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